Just to add to what Vojtech said; you do need internet mail running for Outlook Express, but not the Outlook/Excange provider.
I also can't get rid of P2P, etc. Like you say it seems to work fine using the control panel, then after reboot it goes on the internet and tells me new version 4.1.278 is available (I'm already on 4.1.280, and reinstalling just tells me I'm already up to date), then after the next reboot all the providers are back. It looks like it's attempting a self repair or something.
For now I've given up and am just leaving the extra providers there, but terminated, until someone has other suggestions.
W98SE
Jarron